Conducting heat away from a printed circuit board assembly in an enclosure

ABSTRACT

A printed circuit board assembly (PCBA) is connected to a frame within a passage. The PCBA includes a circuitry package attached to a printed circuit board. The circuitry package has a peripheral edge extending from the printed circuit board to a distal end joined to a cap. A cover is attached to the frame to enclose the PCBA. A thermal interface material (TIM) is disposed between the cover and the PCBA, the TIM defining an opening sized to receivingly engage the circuitry package in a close mating engagement contacting the TIM simultaneously against the cap and the peripheral edge to conduct heat away from the circuitry package. A heat conductor attached to the other side of the printed circuit board in an overlapping opposition to the circuitry package conducts heat away from the printed circuit board that is generated by the circuitry package.

RELATED APPLICATION

This is a continuation-in-part application claiming the benefit of theearlier filing date of U.S. patent application Ser. No. 12/542,502.

FIELD

The present embodiments relate generally to digital data storage, andmore particularly without limitation to conducting heat away from aprinted circuit board assembly in an enclosure of a data storage device.

SUMMARY

Some embodiments of the present invention contemplate an apparatusincluding a frame having a perimeter surface defining a passage. Aprinted circuit board assembly (PCBA) is operably disposed within thepassage. The PCBA includes a printed circuit board and a circuitrypackage attached to one side of the printed circuit board. The circuitrypackage has a peripheral edge and a cap, the peripheral edge extendingfrom a proximal end adjacent the printed circuit board to a distal endjoined to the cap. A cover is attached to the frame to enclose the PCBA.A thermal interface material (“TIM”) is operably disposed between thecover and the PCBA. The TIM defines an opening that is sized toreceivingly engage the circuitry package in a close mating engagementoperably contacting the TIM simultaneously against the cap and theperipheral edge to conduct heat away from the circuitry package.

Some embodiments of the present invention contemplate an apparatusincluding a frame having a perimeter surface defining a passage. A PCBAis operably disposed within the passage. The PCBA includes a printedcircuit board and a circuitry package attached to one side of theprinted circuit board. A cover is operably attached to the frame toenclose the PCBA. A TIM is operably disposed between the cover and thePCBA to conduct heat away from the circuitry package. A heat conductoris attached to the other side of the printed circuit board in anoverlapping opposition to the circuitry package to conduct heat awayfrom the printed circuit board that is generated by the circuitrypackage.

Some embodiments of the present invention contemplate an apparatusincluding a frame having a perimeter surface defining a passage. A PCBAis operably disposed within the passage. The PCBA includes a printedcircuit board and a circuitry package attached to one side of theprinted circuit board. The circuitry package has a peripheral edge and acap, the peripheral edge extending from a proximal end adjacent theprinted circuit board to a distal end joined to the cap. A cover isoperably attached to the frame to enclose the PCBA. A TIM is operablydisposed between the cover and the PCBA, the TIM defining an openingthat is sized to receivingly engage the circuitry package in a closemating engagement operably contacting the TIM simultaneously against thecap and the peripheral edge to conduct heat away from the circuitrypackage. A heat conductor is attached to the other side of the printedcircuit board in an overlapping opposition to the circuitry package toconduct heat away from the printed circuit board that is generated bythe circuitry package.

Some embodiments of the present invention contemplate a methodincluding: obtaining a frame having a perimeter surface defining apassage; obtaining a PCBA having a printed circuit board and a circuitrypackage attached to one side of the printed circuit board, the circuitrypackage having a peripheral edge and a cap, the peripheral edgeextending from a proximal end adjacent the printed circuit board to adistal end joined to the cap; obtaining a TIM defining an opening thatis sized to receivingly engage the circuitry package in a close matingengagement; positioning the TIM on the PCBA in the close matingengagement that contacts the TIM simultaneously against the cap and theperipheral edge; and attaching a cover to the frame to enclose the PCBA.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective depiction of a solid state data storageassembly.

FIG. 2 is an exploded perspective depiction of the solid state datastorage assembly of FIG. 1 constructed in accordance with embodiments ofthe present invention.

FIG. 3 is a perspective depiction of an example printed circuit boardassembly (“PCBA”) of the solid state data storage assembly of FIG. 1.

FIG. 4 is a flow diagram of an example technique for forming the solidstate data storage assembly of FIG. 2.

FIG. 5 is an exploded perspective depiction of the solid state datastorage assembly of FIG. 1 constructed in accordance with embodiments ofthe present invention.

FIG. 6 is a cross-sectional depiction of a portion of the solid statedata storage assembly of FIG. 5.

FIG. 7 is a flow diagram of an example technique for forming the solidstate data storage assembly of FIG. 5.

FIG. 8 is a partially exploded isometric depiction of a portion of thedata storage assembly of FIG. 5.

FIG. 9 is a cross-sectional depiction of the circuitry package of FIG.5.

FIG. 10 is a cross-sectional depiction similar to FIG. 6 but constructedin accordance with alternative embodiments of the present invention.

FIG. 11 is an isometric depiction of the data storage assembly of FIG. 1having an array of fin heat transfer surfaces in the conductive heattransfer path inside the enclosure.

FIG. 12 is a cross-sectional depiction depicting an array of fin heattransfer surfaces extending from the frame and through openings in theexternal cover.

DETAILED DESCRIPTION

Initially, it is to be appreciated that this disclosure is by way ofexample only, not by limitation. The heat transfer concepts herein arenot limited to use or application with any specific system or method forusing storage element devices. Thus, although the instrumentalitiesdescribed herein are for the convenience of explanation, shown anddescribed with respect to exemplary embodiments, it will be appreciatedthat the principles herein may be applied equally in other types ofstorage element systems and methods involving the storage and retrievalof data.

Solid state data storage is an advancing technology for data storageapplications. Solid state data storage devices differ from non-solidstate devices in that they typically have no moving parts and includememory chips to store data. Examples of solid state memory componentsused for solid state data storage include flash memory and magneticrandom access memory (MRAM).

FIG. 1 is a perspective view of an example solid state data storageassembly 10, which can be a non-volatile data storage assembly. Solidstate data storage assembly 10 may also be referred to as a solid-statedrive. Data storage assembly 10 is suitable for use in variousapplications, such as computing devices, portable electronic devices orother devices that store data. Solid state data storage assembly 10differs from non-solid state devices, such as disc drives, in that solidstate data storage assembly 10 typically does not have moving parts.

Data storage assembly 10 includes outer housing 12, which is defined byframe 14, first cover 16, and a second cover 18 (shown in FIG. 2), wherefirst and second covers 16, 18 are mechanically coupled to oppositesides of frame 12 to define a space within which electrical componentsof data storage assembly 10 are enclosed. Covers 16, 18 can bemechanically connected to housing 12 using any suitable technique, suchas using one or more screws, connection fingers, locking/clippingstructures, adhesives, rivets, other mechanical fasteners, welding(e.g., ultrasonic welding) or combinations thereof. Housing 12 may beformed from any suitable material, such as metal (e.g., aluminum),plastic, or other suitable material or combinations thereof. Housing 12substantially encloses at least one printed circuit board assembly(“PCBA,” not shown in FIG. 1), which includes electrical components,such as memory components (e.g., flash memory, magnetic random accessmemory (MRAM), static random access memory (SRAM) or dynamic randomaccess memory (DRAM) chips) that store data and one or more controllers.

FIG. 2 is an exploded perspective view of data storage assembly 10. Theexample data storage assembly 10 shown in FIGS. 1 and 2 includes frame14, first cover 16, second cover 18, PCBA 20, thermal interfaces 22, 24,and label 26. Label 26 may indicate the parameters of data storageassembly 10, e.g., the memory capacity. In other examples, data storageassembly 10 does not include label 26 or may include more than onelabel.

As shown in FIG. 3, which is a schematic illustration of an example PCBA20, PCBA 20 can include printed circuit board 30 and electricalcomponents 32. Electrical components 32 include components such as oneor more controller chips (e.g., controller integrated circuits) thatcontrol the storage and retrieval of data by data storage assembly 10,one or more memory chips (e.g., flash memory, MRAM, SRAM or DRAM chips),one or more passive electrical components (e.g., capacitors orresistors), and the like. Electrical components 32 are electrically andmechanically coupled to printed circuit board 30 using any suitabletechnique, such as using solder joints or connector pins that arepositioned between electrical contacts of electrical components 32 andelectrical contacts on printed circuit board 30. In the example shown inFIG. 3, electrical components 32 are soldered onto printed circuit board20 using a surface mount technology process. As a result, solder joints34 are formed between each electrical component 32 and printed circuitboard 30.

PCBA 20 may include electrical contacts that electrically connect to aplurality of input/output connectors 21, which are each configured toprovide as an interface with one or more host device (e.g., a computer,a consumer electronic device, etc.). For example, input/outputconnectors 21 can be configured to transmit data, power and controlsignals to and from a host device. Example input/output connectors 21can, but need not include a service expansion shelf (SES) connector, aserial advanced technology attachment (SATA) connector, and/or a fourpin test connector. Frame 14 of housing 12 defines opening 15 throughwhich input/output connectors 21 may be accessed. PCBA 20 can also beelectrically connected to additional connectors such as, but not limitedto, a pin connector (e.g., a J1 connector, which is a 110-pinconnector). The additional connectors may be positioned on any suitableside of PCBA 20, such as side 20A substantially opposite side 20B onwhich connector 21 is positioned.

Printed circuit board 30 may include electrical components on more thanone side. Thus, although electrical components 32 are shown on a singleside of printed circuit board 30 in the example shown in FIG. 3, inother examples, electrical components 32 may be positioned on more thanone side of printed circuit board 30 (e.g., on opposite sides of printedcircuit board 30). In addition, although one PCBA 20 is shown in FIG. 2,in other examples, data storage assembly 10 may include any suitablenumber of PCBAs, such as two, three or more. If data storage assembly 10includes a plurality of PCBAs, the PCBAs may be stacked in a z-axisdirection (orthogonal x-y-z axes are shown in FIGS. 1 and 2), stacked inthe x-y plane or any combination thereof.

During operation of data storage assembly 10, heat may be generated byelectrical components 32 of PCBA 20. The generation of heat from theoperation of data storage assembly 10 may be especially compounded whena plurality of data storage assemblies 10 are positioned next to eachother, e.g., in a device or in a server room or other data center. Asheat builds up within housing 12 (FIG. 1), the performance of datastorage assembly 10 may degrade and the useful life of electricalcomponents 32 may decrease due to the added stress on components 32 fromthe relatively high temperature operating environment.

The issue of heat build-up becomes particularly pronounced when housing12 substantially encloses PCBA 20, e.g., as shown in FIGS. 1 and 2, dueto limited air circulation within housing 12 as well as the relativesmall size of housing 12. While one or both covers 16, 18 may be removedfrom data storage assembly 10 in order to help improve the heatconduction of data storage assembly 10, covers 16, 18 serve variouspurposes in assembly 10. As a result, other issues may arise as a resultof removing one or both covers 16, 18 from assembly 10. For example,covers 16, 18 provide shock protection to assembly 10 by increasing thestiffness of assembly 10. In addition, covers 16, 18 helps protect PCBA20 and its electrical components 32 from environmental contaminants,such as dust particles, liquids, and the like. Thus, it may beundesirable to remove covers 16, 18 from housing 12 in some instances.The present embodiments leverage the use the covers 16, 18 as large“single fin” heat sinks by constructing highly thermal conductive pathsfor heat transfer to some or all of the components mounted to theprinted circuit board, which are otherwise thermally insulated from thecovers 16, 18 by being mounted to the printed circuit board.

In order to help improve the heat conduction data storage assembly 10,data storage assembly 10 includes thermal interface 22 positionedbetween PCBA 20 and cover 16, and thermal interface 24 positionedbetween PCBA 20 and cover 18. Thermal interfaces 22, 24 contactdifferent sides of printed circuit board assembly 20. In contrast tothermally insulating material, thermal interfaces 22, 24 each comprise athermally conductive material, which aids in the conduction of heat awayfrom electrical components 32 of PCBA 20 and improves the thermaltransfer efficiency of data storage assembly 10. In some examples,thermal interfaces 22, 24 exhibit a thermally conductivity of about 0.1watts per meter-Kelvin (W/mK) to about 3.0 W/mK, although other thermalconductivities are contemplated. The conduction of heat away fromcomponents 32 can help maintain the operational integrity of electricalcomponents 32 and increase the useful life of data storage assembly 10by decreasing the stress on components 32 that is generated fromrelatively high operating temperatures. In some examples, thermalinterfaces 22, 24 may each comprise a ceramic filled silicone elastomer.However, other thermally conductive materials may also be used to formthermal interfaces 22, 24.

In some examples, thermal interfaces 22, 24 are formed of asubstantially mechanically conformable material, such that thermalinterfaces 22, 24 are capable of substantially conforming to thetopography of PCBA 20. In such examples, when thermal interfaces 22, 24are positioned over PCBA 20 and compressed, thermal interfaces 22, 24may contact one or more surfaces of PCBA 20 (e.g., the surface ofelectrical components 32). Increasing the contact between thermalinterfaces 22, 24 and PCBA 20 with a conformable material may bedesirable in order to increase the conduction of heat away fromelectrical components 32. Furthermore, some of the heat generated by theelectrical components 32 is directed toward and into the printed circuitboard 30, potentially creating a hot spot in the area of the printedcircuit board 30 where the electrical component 32 is mounted. Theconformable material compressingly engaged against the PCBA 20 likewiseconducts heat away from any such hot spot. For the highest powerelectrical components 32, such as controllerapplication-specific-integrated-circuits (“ASICs”), it can beadvantageous to concentrate the hot spot in a thermal via within theprinted circuit board 30, such as metal plates on opposing sides andconductively connected together through the printed circuit board 30.The conformable TIM material 130 in that case can be compressed againstthe metal plate opposing the controller ASIC to enhance the transfer ofheat away from the hot spot.

The materials used in constructing the thermal interfaces 22, 24 areevolving to contain higher percentages of filler materials that enhancetheir thermal conductivity. This has and is expected to even morestiffen the thermal interfaces 22, 24, making them less pliable andhence less capable of conforming completely around an electricalcomponent 32 without leaving a void (air space) between the surface ofthe thermal interface 22, 24 and the surface of the electrical component32. Such voids preclude heat transfer by thermal conduction and therebydiminish the overall thermal conductivity performance of the thermalinterfaces 22, 24. This problem is exacerbated when two or moreelectrical components are closely packed together on the PCBA 20.

In addition to or instead of being formed from a substantiallyconformable material, thermal interfaces 22, 24 may each define aplurality of openings (e.g., cutaway portions) that are configured toreceive surface protrusions of PCBA 20. The surface protrusions may beformed by the placement of electrical components 32 on printed circuitboard 30 and extending from printed circuit board 30. In this way,thermal interfaces 22, 24 may better envelop electrical components 32and increase the surface area for contacting electrical components 32and conducting heat away from electrical components 32.

Thermal interfaces 22, 24 are each formed from one or more layers ofthermally conductive material, which may be substantially continuous inorder to define a path of low thermal resistance. In some examples,thermal interfaces 22, 24 each comprise multiple layers of material thatmay be stacked in a z-axis direction or multiple layers of material thatare positioned adjacent each other in the x-y plane.

In the example of data storage assembly 10 shown in FIG. 2, thermalinterfaces 22, 24 each define a structure having a stiffness thatenables thermal interfaces 22, 24 to be removed from housing 12 whilemaintaining their structural integrity. For example, thermal interfaces22, 24 may each be configured such that they may be removed from housing12 without breaking apart or decomposing upon handling. As a result,thermal interfaces 22, 24 may easily be introduced into and removed fromhousing 12 without generating particles or other contaminants that mayaffect the operation of data storage assembly 10.

Configuring thermal interfaces 22, 24 such that they may each be removedfrom housing 12 without leaving portions of thermally conductivematerial within housing 12 may be useful, e.g., for purposes ofaccessing electrical components 32 (FIG. 3) of PCBA 20. After assemblyof data storage assembly 10, it may be useful to periodically accesselectrical components 32 in order to repair data storage assembly 10 orotherwise rework electrical components 32. Thermal interfaces 22, 24that are removable from data storage assembly 10 without substantiallyadversely affecting the properties of PCBA 20 provides a cost-effectivetechnique for aiding the conduction of heat away from PCBA 20. In someexamples, thermal interfaces 22, 24 may be reused after being removedfrom housing 12 (e.g., may be replaced in housing 12).

Thermal interfaces 22, 24 may have any suitable thickness. In someexamples, thermal interface layers 22, 24 each have a thickness of about0.1 millimeters (mm) to about 2.0 mm. However, other thicknesses arecontemplated and may depend on the dimensions of the particular datastorage assembly 10. As described below, in some examples, a thicknessof each of thermal interface layers 22, 24 may be selected to fill aspace between covers 16, 18 and PCBA 20 within housing 12.

When data storage assembly 10 is assembled, there may be an air gapbetween covers 16, 18 and PCBA 20. This air gap may act as a thermalinsulator that precludes conduction of heat away electrical components32 (FIG. 3). As a result, heat generated by components 32 may beretained within housing 12. In examples in which thermal interfaces 22,24 are sized to fill a space between covers 16, 18, respectively, andPCBA 20, thermal interfaces 22, 24 eliminate the air gaps between covers16, 18 and PCBA 20. Thus, by contacting both covers 16, 18 and PCBA 20,thermal interfaces 22, 24 each provide a relatively low resistancethermal conduction path from PCBA 20, a source of heat, and the exteriorof housing 12 (through covers 16, 18), to which the heat may bedissipated. In this way, data storage assembly 10 is configured suchthat heat can be dissipated through a relatively low resistance thermalpathway including thermal interface material 22, 24, thereby reducingthe operating temperatures within housing 12.

The inclusion of thermal interfaces 22, 24 in housing 12 may increasethe number of potential uses of data storage assembly 10 and/or decreasethe restrictions on the operating environment requirements for datastorage assembly 10. For example, the increased ability of data storageassembly 10 to conduct heat away from electrical components 32 may helpdecrease the cooling requirements for the applications in which datastorage assembly 10 is used. Depending on the application in which datastorage assembly 10 is used (e.g., within a device or a server room), anexternal cooling source (e.g., a fan or an air conditioning unit) may beused to help maintain a desirable operating temperature for data storageassembly 10. The increased ability of data storage assembly 10 toconduct heat away from electrical components 32 may help increase thetolerable operating temperature for data storage assembly 10, which maydecrease the cooling requirements for data storage assembly 10.

In addition to conducting heat away from electrical components 32 ofprinted circuit board assembly 20, thermal interfaces 22, 24 may helpincrease the mechanical robustness of data storage assembly 10. Due tothe configuration and placement of thermal interfaces 22, 24 withinhousing 12, thermal interfaces 22, 24 help protect PCBA 20 from damagedue to the application of a transient or cumulative mechanical load onhousing 12. In this way, thermal interfaces 22, 24 may also be referredto as a shock protector of PCBA 20. As described in further detailbelow, thermal interfaces 22, 24 help increase the stiffness of datastorage assembly 10, as well as limit the movement of electricalcomponents 32 (FIG. 3) relative to printed circuit board 30 (FIG. 3) ofPCBA 20.

Although solid state data storage assembly 10 can exhibit an increasedmechanical robustness compared to disc drives or other data storagedevices with moving parts, solid state data storage assembly 10 maystill be sensitive to applied mechanical loads. That is, thecomparatively higher shock and vibration specifications for the solidstate data storage assembly 10 make it more susceptible to applicationswhere mechanical loading is involved. Mechanical loads may be exerted onhousing 12 of data storage assembly 10, e.g., when data storage assembly10 is dropped or when an external force is applied to housing 12.Printed circuit board 30 may flex or bend (e.g., from a planarconfiguration to a nonplanar configuration) when a shock or another typeof mechanical load is applied to housing 12. The bending or flexing ofprinted circuit board 30 may generate shear stresses that disrupt themechanical joints between electrical components 32 and printed circuitboard 30. For example, if solder joints 34 (FIG. 3) are positionedbetween electrical components 32 and printed circuit board 30 (FIG. 3),the bending or flexing of printed circuit board 30 may result in thedeformation and shearing of solder joints 34. Some shear forces may havea magnitude sufficient to deform at least some of the solder joints 34(or other mechanical connections between electrical components 32 andprinted circuit board 30) to the point of failure. When the mechanicalconnections between electrical components 32 and printed circuit board30 fail, electrical components 32 may break loose from printed circuitboard 30, which disrupts the electrical connection between electricalcomponents 32 and printed circuit board 30, and compromises the abilityof data storage assembly 10 to properly operate.

Note that although the illustrative embodiments of FIG. 3 depict theelectrical components 32 electrically connected to the printed circuitboard 30 by way of external leads the contemplated embodiments are notso limited, in that other types of electrical connections likewisebenefit such as but not limited to using ball grid arrays (“BGAs”) andthe like. Further, although the electrical components 32 are said to besolid state memory components for purposes of an illustrativedescription the contemplated embodiments are not so limited, in thatother types of electrical components likewise benefit such as but notlimited to the controller ASIC that performs top level control of thesolid state memory components. All the advantageous heat transfer andvibration damping described herein is applicable to the controller ASICand other electrical components as well, be they connected with externalleads or BGAs or the like.

In some examples, thermal interfaces 22, 24 may be configured (e.g.,sized and shaped) to help maintain the mechanical and electricalconnection between electrical components 32 and printed circuit board 30of PCBA 20 when a mechanical load is applied to housing 12. Inparticular, in some examples, thermal interfaces 22, 24 are sized andshaped to contact both PCBA 20 and covers 16, 18, respectively, suchthat the stiffness of PCBA 20 is effectively increased. Increasing thestiffness of the PCBA can help maintain the integrity of the electricaland mechanical connections (e.g., connector pins or solder joints)between electrical components 32 (FIG. 3) and printed circuit board 30(FIG. 3) of PCBA 20 by minimizing the stresses that are generated at theelectrical and mechanical connections when a mechanical load is appliedto housing 12.

In particular, positioning thermal interfaces 22, 24 such as thermalinterfaces 22, 24 contacting both PCBA 20 and covers 16, 18,respectively, decreases the possibility that printed circuit board 30will bend or flex when a mechanical load is applied to data storageassembly 10. The contact between covers 16, 18, thermal interfaces 22,24, respectively, and printed circuit board 30 creates a composite orlayered structure that effectively increases the rigidity of datastorage assembly 10 and decreases the amount of available space forcircuit board 30 to flex, thereby discouraging the bending or flexing ofprinted circuit board 30. In this way, the positioning of thermalinterfaces 22, 24 in housing 12 increases the stiffness of PCBA 20,thereby minimizing the magnitude of shear stresses that can result inthe failure of the mechanical joints between the electrical componentsand the printed circuit board.

In some examples, thermal interfaces 22, 24 fill the space between PCBA20 and covers 16, 18, respectively. As a result, when a transientmechanical load is applied to housing 12, thermal interfaces 22, 24 mayhelp hold electrical components 32 in place on printed circuit board 30by limiting the movement of electrical components 32 relative to printedcircuit board 30. This may further help maintain the integrity of theelectrical and mechanical connections (e.g., connector pins or solderjoints) between electrical components 32 (FIG. 3) and printed circuitboard 30 (FIG. 3) of PCBA 20 when a mechanical load is applied tohousing 12.

In addition, in some examples, thermal interfaces 22, 24 help distributea force that is applied to housing 12 across PCBA 20, thereby reducingthe concentration of mechanical stress generated within PCBA 20. In thisway, distributing the force across at least a part of PCBA 20 may reducethe possibility that the mechanical and electrical joints betweenelectrical components 32 and printed circuit board 30 may break due tothe application of external mechanical loads. In some cases, thermalinterfaces 22, 24 also dampen the mechanical loads (e.g., shocks) orvibrations that are applied to housing 12 and transmitted to PCBA 20.For example, thermal interfaces 22, 24 may each be formed of a materialthat has an elastomeric property that enables thermal interfaces 22, 24to absorb some mechanical loads that are applied to housing 12.

In some examples, thermal interfaces 22, 24 are relatively tacky, suchthat when thermal interfaces 22, 24 are positioned between PCBA 20 andcovers 16, 18, respectively, and, sized to fill the space between covers16, 18, respectively, and PCBA 20, thermal interfaces 22, 24 adhere tothe respective cover 16, 18 and PCBA 20. In some examples, at least oneof the thermal interfaces 22, 24 has a peel strength in a range of about0.44 Newton (about 0.1 pound-force) to about 2.22 Newton (0.5pound-force) for a 5.08 centimeter (2 inch) by 8.89 centimeter (3.5inch) sample size relative to PCBA 20. The adhesion between thermalinterfaces 22, 24 and the respective cover 16, 18 and PCBA 20 may alsohelp increase the stiffness of data storage assembly 10, which mayfurther improve the shock protection capability of thermal interfaces22, 24.

In addition, the adhesion between thermal interfaces 22, 24 and therespective cover 16, 18 and PCBA 20 may provide a visible indicationthat data storage assembly 10 has been tampered with. For example, whenthermal interfaces 22, 24 are formed from a relatively tacky material,thermal interfaces 22, 24 may adhere to PCBA 20 and the respective cover16, 18 when data storage assembly 10 is first assembled. However, thematerial from which thermal interfaces 22, 24 are formed may not allowthermal interfaces 22, 24 to re-adhere as well (if at all) to therespective cover 16, 18 and PCBA 20 after data storage assembly 10 isdisassembled. Thus, if cover 16 and thermal interface 22 are separatedfrom the other components of data storage assembly 10, e.g., to gainaccess to electrical components 32 of PCBA 20, such tampering with datastorage assembly 10 may be evidenced by the lack of adhesion or adecrease in adhesion between thermal interface 22 and PCBA 20. The samevisual indication of tampering may also be provided by thermal interface24 if cover 18 and thermal interface 24 are separated from the othercomponents of data storage assembly 10.

It may be desirable to determine whether the internal components of datastorage assembly 10 were exposed, thereby indicating tampering withelectrical components 32, for various purposes. For example, themanufacturer of data storage assembly 10 may provide a buyer with alimited warranty (e.g., covering manufacturing defects), which may benullified if the data storage assembly 10 is tampered with. Prior toperforming any warranty repairs on a data storage assembly 10, themanufacturer may determine whether data storage assembly 10 has beentampered with by examining the adhesion between thermal interfaces 22,24 and covers 16, 18, respectively, and PCBA 20. A diminished adhesion(e.g., compared to an expected adhesion) between one or both of thethermal interfaces and PCBA 20 may indicate that the thermal interfacehas been removed from housing 12 and subsequently replaced in housing12.

If thermal interfaces 22, 24 are formed from a substantially conformablematerial, the manufacturer may also visually inspect thermal interfaces22, 24 to determine whether the pattern defined by the surface ofthermal interfaces 22, 24 facing PCBA 20 substantially matches theexpected pattern of a thermal interface 22 that has been first removedfrom housing 12. If pattern defined by the surface of one or boththermal interfaces 22, 24 differs from the expected pattern, it mayindicate that the thermal interface has been removed from housing 12 andsubsequently replaced in housing 12, thereby indicating data storageassembly 10 has been tampered with.

Example

An experiment was performed to compare the shock resistance of a solidstate drive assembly including a thermally conductive interface materialcompared to a solid state drive assembly that is otherwise similar, butdoes not include a thermally conductive interface material. A ½ sinepulse shock was applied to a solid state drive assembly including ahousing similar to housing 12 shown in FIGS. 1 and 2 and a PCBAincluding a plurality of electrical components soldered to a printedcircuit board. In particular, a solid state drive assembly was droppedusing a Lansmont Drop Tester (made available by Lansmont Corporation ofMonterey, Calif.), which helped maintain the desired orientation of thesolid state drive assembly as it was dropped. The acceleration at whichthe drive assemblies were dropped was determined using Model 352A25 andModel 352C22 accelerometers (made available by PCB Piezotronics, Inc. ofDepew, N.Y.).

A plurality of solid state drive assemblies each having a differentprinted circuit board thickness and excluding a thermal interfacematerial were dropped in various orientations. Table 1 illustrates theaccelerations with which the solid state drive assemblies were dropped,the thickness of the printed circuit board of the solid state driveassembly, and a duration of each of the drops.

TABLE 1 Z-axis Y-axis X-axis Duration Printed Acceleration AccelerationAcceleration of Load Circuit Board Iteration ( G) (G) ( G) ApplicationPass/Fail Orientation Thickness 1 1500 G 0 0 0.52 ms Pass Memory ArrayUp 0.76 mm 2 1500 G 0 0 0.52 ms Pass Memory Array Up 0.76 mm 3 1567 G 00 0.52 ms Fail Memory Array Up 0.76 mm 4 1508 G 0 0 0.52 ms Pass MemoryArray Up 0.94 mm 5 0 1537 G 0 0.51 ms Pass I/O Connector down 0.94 mm 60 0 1584 G 0.51 ms Pass Four pin 0.94 mm Connector Up 7 0 0 −1332 G 0.52 ms Pass Four pin 0.94 mm Connector Down 8 0 −1523 G  0 0.50 ms PassI/O Connector Up 0.94 mm 9 −1534 G  0 0 0.52 ms Fail Memory Array Down0.94 mm 10 1521 G 0 0 0.50 ms Pass Memory Array Up 1.20 mm 11 0 1618 G 00.48 ms Pass I/O Connector down 1.20 mm 12 0 0 1385 G 0.48 ms Pass Fourpin 1.20 mm Connector Up 13 0 0 −1449 G  0.47 ms Pass Four pin 1.20 mmConnector Down 14 0 −1440 G  0 0.48 ms Pass I/O Connector Up 1.20 mm 15−1514 G  0 0 0.50 ms Fail Memory Array Down 1.20 mm

In each of the iterations, the solid state drive assembly was droppedwith the solid state drive assembly oriented such that the electricalcomponents were facing in either a positive z-axis direction (“memoryarray up”) or a negative-z-axis direction (“memory array down”), suchthat the input-output (I/O) connector of the solid state drive assemblywas face down (e.g., electrical components facing in positive y-axisdirection) or face up (e.g., electrical components facing in negativey-axis direction), or such that a four pin connector of the solid statedrive assembly was face up (e.g., electrical components facing inpositive x-axis direction) or face down (e.g., electrical componentsfacing in negative x-axis direction). In each of the solid state driveassemblies that were dropped, the four pin connector and the I/Oconnector are positioned on opposite sides of a housing of the solidstate drive assembly.

Iterations 1-3 shown in Table 1 represent the dropping of three solidstate drive assemblies each having a printed circuit board thickness ofabout 0.76 millimeters (mm). Iterations 4-9 shown in Table 1 representthe dropping of a single solid state drive assembly having a printedcircuit board thickness of about 0.94 mm. In each subsequent drop foriterations 4-9, the solid state drive assembly was rotated, such thatthe consequences of dropping the solid state drive assembly in each of aplurality of orientations was determined. Iterations 10-15 shown inTable 1 represent the dropping of a single solid state drive assemblyhaving a printed circuit board thickness of about 1.20 mm. In eachsubsequent drop for iterations 10-15, the solid state drive assembly wasrotated, such that the consequences of dropping the solid state driveassembly in each of a plurality of orientations was determined.

A solid state drive assembly was considered to fail the shock test if,upon visual inspection, any of the electrical components were loose orhad fallen off the printed circuit board of the solid state driveassembly. As Table 1 demonstrates at least some of the solid state driveassemblies that did not include a thermal interface material were unableto withstand the applied shock. In particular, the solid state driveassemblies showed a sensitivity to accelerations in a negative z-axisdirection.

A solid state drive assembly similar in configuration to those tested togenerate the data shown in Table 1 was modified to include a thermalinterface material between the covers of the housing and the PCBA. Thethermal interface material was Bergquist Gap Pad 2202, which isavailable from Bergquist Company of Chanhassen, Minn., and was selectedto have a thickness of about 0.051 mm (about 0.020 inches) to fill thespace between the covers of the housing and the PCBA. The solid statedrive assembly including a thermal interface material was dropped fivetimes using the Lansmont Drop Tester to determine whether the thermalinterface material helped improve the ability of the solid state driveassembly to withstand a shock applied to the outer housing.

Table 2 illustrates the various accelerations with which the solid statedrive assembly was dropped, as well as the thickness the printed circuitboard and a duration of the drop. As with the testing performed togenerate the data shown in Table 1, the solid state drive assembly wasconsidered to fail the shock test if, upon visual inspection, any of theelectrical components (e.g., memory chips) were loose or had fallen offthe printed circuit board of the solid state drive assembly.

TABLE 2 Z-axis Y-axis X-axis Duration Printed Acceleration AccelerationAcceleration of Load Circuit Board Iteration (G) (G) (G) ApplicationPass/Fail Orientation Thickness 1 −1513 G 0 0 0.52 ms Pass Memory ArrayUp 1.20 mm 2 −1637 G 0 0 0.52 ms Pass Memory Array Up 1.20 mm 3 −1765 G0 0 0.52 ms Pass Memory Array Up 1.20 mm 4 −1867 G 0 0 0.52 ms PassMemory Array Up 1.20 mm 5 −1957 G 0 0 0.52 ms Pass Memory Array Up 1.20mm

As Table 2 demonstrates, the solid state drive assembly including athermal interface material positioned between the covers of the housingand the printed circuit board assembly was able to withstandaccelerations up to 1957 G when the solid state drive assembly wasdropped with the electrical components (e.g., the memory array) facingin a positive z-axis direction. This suggests that the thermal interfacematerial improves the shock protection of a solid state drive assembly,and, in particular, the electrical components of a PCBA.

FIG. 4 is a flow diagram of an example technique for forming solid statedata storage assembly 10. In accordance with the technique shown in FIG.4, one or more PCBAs 20 are placed within frame 14 (40). The one or morePCBAs 20 can be attached to frame 14 using any suitable technique. Insome examples, frame 14 includes side rails, brackets or othermechanical structures that align with and support the one or more PCBAs20. The one or more PCBAs 20 can be mechanically connected to these siderails, brackets or other mechanical structures of frame 14. For example,the one or more PCBAs can be connected to frame 14 using one or morescrews, connection fingers, locking/clipping structures, adhesives,rivets, other mechanical fasteners, welding (e.g., ultrasonic welding)or combinations thereof.

After placing one or more PCBAs 20 within frame 14, thermally conductivematerial defining thermal interface 22 is placed over PCBA 20 (42). Insome examples, the thermally conductive material is placed over PCBA 20such that the major surface of PCBA 20 that is exposed by frame 14 issubstantially covered by the thermally conductive material. In this way,thermal interface 22 may be sized and shaped to substantially cover PCBA20. After the thermally conductive material is placed over PCBA 20 todefine thermal interface 22 (42), cover 16 is positioned over thermalinterface 22 (44) and attached to frame 14 (46). Cover 16 can beattached to frame 14 using any suitable technique, such as screws,connection fingers, locking/clipping structures, adhesives, rivets,other mechanical fasteners, welding (e.g., ultrasonic welding) orcombinations thereof.

Thermally conductive material can be pre-attached to cover 16 or canseparate from cover 16 prior to inclusion in housing 12. In someexamples, thermal interface 22 has a thickness that is greater than orequal to a distance between cover 16 and PCBA 20. As a result, whencover 16 is positioned over thermal interface 22 (44) and attached toframe 14 (46), thermal interface 22 substantially fills the spacebetween cover 16 and PCBA 20. In addition, in examples in which thermalinterface 22 has a thickness that is greater than a distance betweencover 16 and PCBA 20, the attachment of cover 16 to frame 14 compressesthermally interface 22, which may further increase the stiffness of datastorage assembly 10. As discussed above, this may help reduce thepossibility that printed circuit board 30 (FIG. 3) bends or flexes inthe z-axis direction, which can help maintain the integrity of themechanical and electrical connection between electrical components 32(FIG. 3) and printed circuit board 30.

In some examples of data storage assembly 10, housing 12 may include asingle cover. In other examples, however, housing 12 of data storageassembly 10 includes two covers (e.g., as shown in FIG. 1) or more thantwo covers. Thus, in some examples of the technique shown in FIG. 4, athermal conductive material may also be placed over the opposite surfaceof PCBA 20 to define second thermal interface 24, and second cover 18may subsequently be positioned over second thermal interface 24 andattached to frame 14.

There being “more than two covers” generally contemplates embodiments inwhich there can be one or more internal cover(s) in addition to the twoexternal covers 16, 18 discussed above. Also as previously discussed,some embodiments contemplate the data storage assembly having aplurality of PCBAs in the same enclosure. FIG. 5 is an explodedperspective depiction of illustrative embodiments in which the frame 14a has a perimeter surface 50 defining a passage 52 into which two PCBAs20 a, 20 b can fit. As discussed previously, each of the PCBAs 20 a, 20b has a plurality of solid state memory components (“components”) 32, aswell as other electronic components, operably generating heat that isnecessarily controlled in accordance with embodiments of this invention.As described above, the thermal interface 22 contactingly engages andthereby conducts heat away from the components 32 during theiroperation. That is, the thermal interface 22 conducts the heat to thecover 16 which sheds the heat load by convection, such as can beenhanced by a directed airflow over the data storage assembly enclosure.

However, heat can build up in the space inside the enclosure on theother side of the PCBA 20 a, especially where components 32 are mountedon that opposing side of the PCBA 20 a. The data storage assembly 10 ais incapable of conductively shedding heat from the components 32 on theopposing side of the PCBA 20 a; it is a dead air space. Clarifying, forpurposes of this description and meaning of the appended claims the term“dead air space” is an area inside the enclosure where there is noconductive heat transfer path from the components 32 to the enclosure.The components 32 are attached to the printed circuit board 30 whichmight, in turn, be in contact with the enclosure. However, the printedcircuit board 30 is not intended, and hence not constructed, to be athermally conductive structure and as such does not provide asignificant conductive heat transfer path directly from a selectedcomponent 32 to the external enclosure as that term “thermallyconductive structure” is meant in accordance with these embodiments.That is, although the printed circuit board 30 includes metallic tracesforming electrical circuitry, and those metallic traces do conduct heatgenerated by the components 32, the embodiments of the present inventioncontemplate thermally conductive structures that conduct heat away fromthe components 32 along non-electrical pathways to prevent the buildupof deleterious heat in the electrical circuitry and in adjacentcomponents 32 connected to the electrical circuitry. The heat load inthe dead air space is exacerbated when both of the sides of the PCBAs 20a, 20 b forming the dead air space have mounted components 32 thatoperably generate heat.

To conduct heat out of the dead air space an internal cover 54 isdisposed within the passage 52 on the opposing side of the PCBA 20 afrom the external cover 16. It will be noted that here the internalcover 54 and the external cover 16 are substantially parallel to eachother, and that they cooperate with the frame 14 a to enclose the PCBA20 a. The internal cover 54 is constructed of a rigid layer 56 that isthermally conductive, such as made of steel or aluminum and the like. Inthese illustrative embodiments the rigid layer 56 is connected in directcontact with the frame 14 a, and for that reason the frame 14 a islikewise constructed of a thermally conductive material such as aluminumor steel and the like.

FIG. 6 is a partial cross-sectional depiction of the data transferassembly 10 a depicting the frame 14 a defining a protuberant rail 58extending from the peripheral surface 50. The protuberant rail 58includes an upper (as depicted here) surface 60 upon which the rigidlayer 56 is supported. A compressible conductive layer 62, such as usedin constructing the thermal interfaces 22, 24, is compressinglysandwiched between the rigid layer 56 and the PCBA 20 a. Thecompressible conductive layer here and elsewhere is sometimes referredto as the thermal interface material (“TIM”). For example, withoutlimitation, the compressible conductive layer 62 can be adhered orotherwise joined to the rigid layer 56, or the compressible conductivelayer 62 can be stacked onto the rigid layer 56. An attachment feature64 in the rail 58, such as the depicted threaded bore, can be sized toreceivingly engage a fastener 66 that attaches both the external cover16 and the internal cover 54, as well as the sandwiched compressiblemembers 62, 22, respectively, to the frame 14 a. The contactingengagement of the compressible conductive layer 62 creates a thermallyconductive path for conducting heat from the component 32 to the rigidlayer 56. The contacting engagement of the rigid layer 56 against theprotuberant rail 58 extends that thermally conductive path forconducting heat to the external surface of the rail 14 a where the heatcan be shed by convection to the surrounding environment. The entirepath for conducting heat from the component 32 is depicted by theenlarged arrow 67.

In the same way in these embodiments another internal cover 70 (FIG. 5)is parallel to the external cover 18 on opposing sides of the PCBA 20 b,such that the covers 70, 18 and the frame 14 a enclose the PCBA 20 b.The internal cover 70 has a rigid layer 72 constructed like the rigidlayer 56. A surface 73 of the protuberant rail 58 provides a lower (asdepicted here) surface against which the rigid layer 72 is supported.The gap between the rigid layers 56, 72, as defined by the height (asdepicted here) of the protuberant rail 58, can be sized as appropriatefor clearance purposes of the overall assembly such as to provide spacefor one or more electrical connectors joining the PCBAs 20 a, 20 btogether.

A compressible conductive layer 74, like the compressible conductivelayer 62, is compressingly sandwiched between the rigid layer 72 and thePCBA 20 b. As before, the compressible conductive layer 74 can beadhered or otherwise joined to the rigid layer 72, or the compressibleconductive layer 74 can be stacked onto the rigid layer 72. Anotherattachment feature 64, such as the depicted threaded bore, can be sizedto receivingly engage a fastener 66 that attaches both the externalcover 18 and the internal cover 70, as well as the sandwichedcompressible members 74, 24, respectively, to the frame 14 a. Thecontacting engagement of the compressible conductive layer 74 creates athermally conductive path for conducting heat from the component 32 tothe rigid layer 72. The contacting engagement of the rigid layer 72against the protuberant rail 58 extends that thermally conductive pathfor conducting heat to the external surface of the rail 14 a where theheat can be shed by convection to the surrounding environment. Theentire path for conducting heat from the component 32 is depicted by theenlarged arrow 67.

The protuberant rail 58 and open passage 52 arrangement advantageouslysimplifies the manufacturing methodology employed to assemble the datastorage assembly 10 a. FIG. 7 is a flow diagram of an illustrativetechnique for forming the solid state data storage assembly 10 a. Inthese embodiments the frame 14 a is suitably supported, such as in anassembly fixture and the like, such that the internal cover 54 ispositioned within the passage 52 and supported upon the rail 58 (100).The frame 14 a can advantageously be positioned horizontally in orderthat gravity can assist in positioning the internal cover 54 on the rail58. From the above description it is noted that the internal cover 54can include both the rigid layer 56 and the compressible conductivelayer 62, so either the layers 56, 62 are positioned as a unitaryassembly or they are positioned individually and in order (100). ThePCBA 20 a is then positioned within the passage 52 upon the internalcover 54 (102). The external cover 16 is then positioned against theframe 14 a (104). In embodiments where the compressible thermalinterface 22 is included then the layers 16, 22 are either positioned asa unitary assembly or the layers 16, 22 are positioned individually andin order. A plurality of fasteners 66 are then coupled at distal endsthereof to the respective attachment features 64 in the rail 58 toattach both covers 54, 16 and the PCBA 20 a to the rail 58, and to alsocompressingly sandwich the thermal interface materials 62, 22therebetween (106).

With the top (as depicted) half assembled a determination is then madeas to whether the other side needs to be assembled (108). If thedetermination is “no,” then the technique ends. Otherwise, if thedetermination is “yes,” then optionally the frame 14 a can berepositioned to facilitate the further assembly operations (110). Forexample, if the frame 14 a is positioned horizontally during theassembly above for the advantage of using gravity to assist inpositioning the components of assembly, then the frame 14 a can berotated 180 degrees so that it is presented in the same advantageousposition for assembling the rest of the components of assembly.

In any event, control returns to the beginning of the technique suchthat the internal cover 70 is positioned within the passage 52 andsupported upon the rail 58 (100). Again, from the above description itis noted that the internal cover 70 can include both the rigid layer 72and the compressible conductive layer 74, so either the layers 72, 74are positioned as a unitary assembly or they are positioned individuallyand in order (100). The PCBA 20 b is then positioned within the passage52 upon the internal cover 70 (102). The external cover 18 is thenpositioned against the frame 14 a (104). In embodiments where thecompressible thermal interface 24 is included then the layers 18, 24 areeither positioned as a unitary assembly or the layers 18, 24 arepositioned individually and in order. A plurality of fasteners 66 arethen coupled at distal ends thereof to the respective attachmentfeatures 64 in the rail 58 to attach both covers 70, 18 and the PCBA 20b to the rail 58, and to also compressingly sandwich the thermalinterface materials 74, 24 therebetween (106).

All of the foregoing embodiments employing internal covers 54, 70 areused in an enclosure that is constructed of two external covers 16, 18,although the contemplated embodiments are not so limited. In equivalentalternative embodiments of a data storage assembly (not depicted) aunitary closed-bottom frame can be employed with the components ofassembly described above assembled in the same arrangement but frombottom-up. Instead of the protuberant rail or some like attachmentfeature extending from the frame, a spacer can be included in the stackbetween the rigid layers of the opposing internal covers.

FIG. 8 is an exploded isometric depiction of the component 32 in themanner that it is typically found in the form of a protuberant cuboidextending from the substantially planar surface of the printed circuitboard 30. FIG. 9 is cross-sectional diagrammatic depiction of thecomponent 32 more particularly shown as an integrated circuit (“IC”)over molded package 32, or also referred to herein generally as acircuitry package 32. The circuitry package 32 has a substrate 100 uponwhich an IC chip 102 is electrically connected by a plurality ofinternal connections such as solder joints 104 between correspondingleads or contacts embedded in underfill 105. The substrate 100 has anumber of electrical traces, layers, and vias (not depicted) tocommunicate with the input/output (“I/O”) signal traces of the IC chip102 by a number of external connections 106, such as the ball grid array106 depicted in these illustrated embodiments. The ball grid array 106is arranged to be connected to corresponding electrical traces orcontacts on the printed circuit board 30 (not depicted in FIG. 9).

The IC chip 102 is enclosed by the over molded package constructed by aperipheral edge 108 that extends from a proximal end 110 adjacent theprinted circuit board 30 to a distal end 112. A cap 114 spans the distalend 112 to cooperatively enclose the IC chip 102.

Returning momentarily to FIG. 6 it will be understood that in thoseembodiments the square corners of the circuitry package 32 compress thethermal interface material (“TIM”) 22, 24, 62, 74 such that there isconsistent contact between the cap 114 and the TIM but there is an airgap between the peripheral edge 108 and the TIM. It has been determinedthrough reduction to practice of the present embodiments thatsignificantly improved thermal heat transfer of heat away from thecircuitry package 32 can be accomplished by modified embodiments of theTIM that eliminate the air gaps in the embodiments depicted by FIG. 6,instead providing consistent physical contact of the TIM against theentire peripheral edge 108 of the circuitry package 32.

FIG. 9 also depicts a modified TIM 116 that is flipped upside-down withrespect to its operable orientation relative to the circuitry package32. The TIM 116 is operably disposed between one of the covers 16, 18,56, 72 and the corresponding PCBA 20 a, 20 b as described in FIG. 6. TheTIM 116 has a planar surface 118 that contactingly engages the printedcircuit board 30 as described in FIG. 6. However, the TIM 116 generallydefines an opening 120 that is sized to receivingly engage the circuitrypackage 32 in a close mating engagement. That is, in these illustrativeembodiments in which the circuitry package 32 is a protuberant cuboid,the TIM 116 has upstanding (as depicted) sides 122 terminating at aplanar top surface 124 cooperatively defining the opening 120. Note thatthe depth 126 of the opening 120 is less than the thickness 128 of theTIM 116 so that the TIM 116 is compressed between the cap 114 and therespective cover 16, 18, 56, 72. In some embodiments the openings can beformed, such as molded, into the TIM such that it is unitarilyconstructed. Alternatively, the TIM can be constructed by joining twolayers, one layer defining the opening and the other layer being solid.

FIG. 10 is a view similar to FIG. 6 but depicting the TIM 116compressingly sandwiched between the cover 16 and the PCBA 20 a. Theopening 120 in the TIM 116 advantageously receivingly engages thecircuitry package 32 in the close mating engagement operably contactingthe TIM 116 simultaneously against the cap 114 and against theperipheral edge 108 to conduct heat away from the circuitry package 32.

Note that in these illustrative embodiments the peripheral edge 108extends substantially orthogonally to the printed circuit board 30. Inalternative equivalent embodiments the shape of the peripheral edge canvary, in such case the opening in the TIM is altered to receive thecircuitry package in the close mating engagement that simultaneouslycontacts both the peripheral edge (sides) and the cap (top) of thecircuitry package. The package edge and cap can be formed any of anumber of ways such as the top being a separate component or moldedaltogether, and such as defining a flat top surface or a top hat steppedsurface. In the case of a flip chip the top hat shape is formed bystacking two dies. Likewise, in these illustrative embodiments the capis substantially parallel to the printed circuit board but thecontemplated embodiments are not so limited. In the same manner, inalternative embodiments the cap can vary and in such case the TIM isaltered to receive the circuitry package in the close mating engagement.

Note as well that the foregoing described one opening in the TIM for onecircuitry package, but the contemplated embodiments are not so limited.For example, it is contemplated in the embodiments of FIG. 5 that theTIM 22 has a plurality of openings sized and arranged to receivinglyengage many or all of the circuitry packages 32 as well as othercomponents shown on the top side (as depicted) of the PCBA 20 a. In someembodiments the size of one such opening is a different size thananother one of the openings.

FIG. 10 also depicts a heat conductor 130 attached to the other side ofthe printed circuit board 30 in the PCBA 20 a instead of anothercircuitry package 32. In some circumstances the heat generated by one ofthe circuitry packages 32 is high enough that it must be controllablysegregated from other components on the PCBA. For example, thecontroller application-specific-IC (“ASIC”) in the solid-state drive(“SSD”) previously described consumes a lot of power and concomitantlygenerates a lot of heat.

A significant part of the heat flux is downward (as depicted) from theIC 102 (FIG. 9) into the substrate 100 and, in turn, into the printedcircuit board 30 to which it is attached. The thermal conduction throughthe cap 114 into the cover 16 cannot remove all the downward-directedheat flux, such that the printed circuit board 30 can become a hot spot.Left unchecked, the hot spot can cause a rise in junction temperature ofthe controller ASIC, degrading efficiency and resulting in even morepower consumption which becomes a potential failure mode for runawaytemperature. The hot spot can also migrate to adjacent electroniccomponents which cannot be expected to operate reliably at or aboverated case temperatures.

The heat conductor 130 resolves any hot spot concerns by conducting heatfrom the printed circuit board 30 to the internal cover 56 which, asdescribed above, conducts the heat to the frame 14 a where it can beshed by convection to the external environment. Preferably, the heatconductor 130 is constructed of a highly conductive material such as anon-compressible layer of aluminum or similar metal.

The heat conductor 130 is attached to the printed circuit board 30 inoverlapping opposition to the circuitry package 32 in order to conductheat away that is generated by the circuitry package 32. That is, by“overlapping opposition” it is meant that the heat conductor 130 and thecircuitry package 32 overlap each other at least partially on oppositesides of the printed circuit board 30. This defines a proximity of theheat conductor 130 to the source of the heat it is designed to conductaway from the PCBA.

It is not unusual that these high operating temperature circuitrypackages, such as the SSD controller ASIC, are constructed of a flipchip 32 a in the PCBA 20 b in FIG. 10. The flip chip 32 a is constructedof one IC 134 being electronically connected to another IC 136 which, inturn, is electronically connected to the printed circuit board 30 in thePCBA 20 b. In this event, as described above, the opening 120 a in theTIM 24 is configured with a step to receivingly engage the flip chip 32a in the close mating engagement that contacts the TIM 24 against bothperipheral edges 138, 140 and against both caps 142, 144 of the ICs 134,136, respectively.

Another heat conductor 146 is attached to the PCBA 20 b in overlappingopposition to the flip chip 32 a. The heat conductor 146 is constructedof a non-compressible portion 148 that can be selected to optimize thethermal conductivity performance, such as by making it of aluminum asdescribed. The non-compressible portion 148 is attached to acompressible layer 150, such as another layer of TIM 150. In alternativeequivalent embodiments (not depicted) the heat conductor can have two ormore layers of TIM, such as but not limited to a non-compressibleportion sandwiched between opposing layers of TIM. The compressibilityof the heat conductor 146 advantageously maintains positive contactingengagements throughout various tolerance ranges of the built up stack.Employing the TIM 150 against the PCBA 20 b can also be advantageouswhere the surface of the PCBA 20 b is not entirely free of componentssuch as traces or contacts and the like. In alternative equivalentembodiments the compressibility can be constructed of two individuallynon-compressible members, such as telescoping members biased away fromeach other against the PCBA 20 b and the internal cover 72, or a springmember, and the like.

Generally, the present embodiments contemplate conducting heat away fromthe PCBA inside the enclosure so that the heat can be shed by convectiveheat transfer to the surrounding environment. Various heat conductivepaths are described by which heat that is generated by a circuitrypackage is transferred to the outermost enclosure where the convectivetransfer is possible. For example, the internal cover 56 conducts heatto the frame 14 a that originates from the circuitry package 32. Theframe 14 a conducts that heat (originating from the circuitry package32) to the external surfaces of the enclosure; that is, to the externalsurface of the frame 14 a and to the external surfaces of the externalcovers 16, 18. Forced and free convective air flow over those externalsurfaces of the enclosure transfers the heat away from the enclosure.The convective heat transfer capability is proportional to the exposedexternal surface area of the enclosure.

In some embodiments an array of fin surfaces is included in the path ofthermal conduction to increase the external surface area of theenclosure, and to thereby enhance the rate at which the heat can beconvectively shed to the external environment. FIG. 11 depictsillustrative embodiments in which an array of parallel upstanding finsurfaces 152 are formed as a part of the external cover 16, and therebydisposed in the path of thermal conduction that begins inside theenclosure from the component 32 and ultimately extends to the outersurface of the external cover 16. The illustrative embodiments of FIG.11 depict a comparatively small portion of the external cover 16 formingthe protuberant fin surfaces 152, but the contemplated embodiments arenot so limited. In equivalent alternative embodiments the fin surfacescan form a different area up to the entire surface area of one or bothexternal covers as well as from the external surface of the frame.

Furthermore, the fin surfaces 152 are formed as a portion of theexternal cover 16. FIG. 12 depicts alternate embodiments wherein the finsurfaces 152 a are formed as a portion of the frame 14 b and extendthrough appropriately sized openings in the external cover 16 a. Again,these depicted embodiments are illustrative and not limiting in thatalternatively equivalent embodiments contemplate the fin surfaces 152 aextending through one or both external covers and/or along theexternally exposed surface of the frame. In yet other equivalentalternative embodiments a heat sink can be attached at a proximal end toa component 32, such as the controller ASIC, and such as with the TIMsandwiched therebetween, with the heat sink extending through anappropriately sized opening in the external cover(s) to provide finsurfaces at the distal end thereof.

FIG. 12 also generally depicts the manner in which the enclosure height(“H”) of the solid-state assembly can be effectively increased by theprotuberant fin surfaces 152 a to provide a standard form factor (“F”)of the enclosure/fin combination. For example, without limitation,reductions to practice of these embodiments have converted a single PCBA2.5 inch by 7-millimeter (H=7 mm) form factor solid-state assembly intoa 2.5-inch by 9.5 mm (F=9.5 mm) form factor by the protuberant extensionof the fin surfaces 152 a from the enclosure. Likewise, the 7 mm formfactor can be extended to the 12.7 mm or 15 mm form factors byadditional protuberant extensions of the fin surfaces 152 a. In the samemanner a dual PCBA 2.5 inch by 12.7 mm form factor solid state assemblycan be effectively increased to a 15 mm form factor by the additionalprotuberant extensions of the fin surfaces 152 a.

The illustrative embodiments depict elongated parallel fins defining thefin surface arrays, but the contemplated embodiments are not so limited.In alternative embodiments freestanding protuberant posts, such as roundor square and the like, can be used to advantageously be exposed toconvective airflow in multiple directions as opposed to the singleairflow direction accommodated by the valley formed between the adjacentelongated fins depicted.

It is to be understood that even though numerous characteristics andadvantages of various embodiments of the present invention have been setforth in the foregoing description, together with the details of thestructure and function of various embodiments of the invention, thisdisclosure is illustrative only, and changes may be made in detail,especially in matters of structure and arrangement of parts within theprinciples of the present invention to the full extent indicated by thebroad general meaning of the terms in which the appended claims areexpressed. For example, any single or multiple pluralities of thecircuit packages and corresponding TIM openings, as well as the heatconductors, and various arrangements thereof are contemplated whilestill maintaining substantially the same functionality without departingfrom the scope and spirit of the claimed invention. For example withoutlimitation the contemplated embodiments include stand-alone TIMs withindividual openings as well as the disclosed sheet of TIM with multipleopenings. For another example without limitation there can be differentnumbers of circuit packages and corresponding heat conductors; there canbe more than one heat conductor for a circuitry package, or one heatconductor can span more than one circuitry package. Further, althoughthe preferred embodiments described herein are directed to data storagedrives, and related technology, it will be appreciated by those skilledin the art that the claimed invention can be applied to other devicesemploying heat generating components, without departing from the spiritand scope of the present invention.

1. An apparatus comprising: a frame having a perimeter surface defining a passage; a printed circuit board assembly (PCBA) operably disposed within the passage, the PCBA including a printed circuit board and a circuitry package attached to one side of the printed circuit board, the circuitry package having a peripheral edge and a cap, the peripheral edge extending from a proximal end adjacent the printed circuit board to a distal end joined to the cap; a cover attached to the frame to enclose the PCBA; and a thermal interface material (“TIM”) operably disposed between the cover and the PCBA, the TIM defining an opening that is sized to receivingly engage the circuitry package in a close mating engagement operably contacting the TIM simultaneously against the cap and the peripheral edge to conduct heat away from the circuitry package.
 2. The apparatus of claim 1 wherein the TIM opening, prior to the TIM contacting the circuitry package, is defined by a TIM surface matching the peripheral edge of the circuitry package that extends substantially orthogonally to the printed circuit board.
 3. The apparatus of claim 1 wherein the TIM opening, prior to the TIM contacting the circuitry package, is defined by a TIM surface matching the cap of the circuitry package that is substantially parallel to the printed circuit board.
 4. The apparatus of claim 1 comprising a heat conductor attached to the other side of the printed circuit board in an overlapping opposition to the circuitry package to conduct heat away from the printed circuit board that is generated by the circuitry package.
 5. The apparatus of claim 1 wherein the PCBA is characterized by a plurality of circuitry packages and the opening is sized for a first circuitry package of the plurality, further comprising the TIM defining a second opening that is sized for the close mating engagement with a second circuitry package of the plurality.
 6. The apparatus of claim 1 wherein the opening is molded into the TIM prior to the TIM contacting the circuitry package.
 7. The apparatus of claim 1 wherein the circuitry package is characterized as a first circuitry package that is attached to a second circuitry package forming a flip-chip package, the TIM, prior to contacting the flip-chip package, having first surfaces defining the opening that operably contact the cap and the peripheral edge of the first circuitry package and the TIM further having a different second surface that operably contacts the second circuitry package.
 8. The apparatus of claim 7 wherein one of the TIM first surfaces that operably contacts the cap is substantially parallel to the second surface.
 9. The apparatus of claim 4 wherein the cover is characterized as an external cover, further comprising an internal cover within the passage and enclosing the PCBA, the internal cover contacting the heat conductor and the frame to conduct heat generated by the circuitry package from the heat conductor to the frame.
 10. An apparatus comprising: a frame having a perimeter surface defining a passage; a printed circuit board assembly (PCBA) operably disposed within the passage, the PCBA including a printed circuit board and a circuitry package attached to one side of the printed circuit board; a cover operably attached to the frame to enclose the PCBA; a thermal interface material (“TIM”) operably disposed between the cover and the PCBA to conduct heat away from the circuitry package; and a heat conductor attached to the other side of the printed circuit board in an overlapping opposition to the circuitry package to conduct heat away from the printed circuit board that is generated by the circuitry package.
 11. The apparatus of claim 10 wherein the cover is characterized as a first cover, comprising a second cover operably attached to the frame to enclose the PCBA.
 12. The apparatus of claim 11 wherein the heat conductor is a non-compressible structure operably disposed between the second cover and the PCBA.
 13. The apparatus of claim 12 wherein the heat conductor comprises a metal.
 14. The apparatus of claim 11 wherein the heat conductor is a compressible structure operably disposed between the second cover and the PCBA.
 15. The apparatus of claim 11 wherein the TIM is characterized as a first TIM, the heat conductor comprising a second TIM structure attached to a non-compressible structure.
 16. The apparatus of claim 11 wherein the heat conductor defines a plurality of heat transfer fin surfaces.
 17. The apparatus of claim 16 wherein the fin surfaces extend from an external surface of the first cover.
 18. The apparatus of claim 16 wherein the heat transfer fin surfaces are sized to define a standard form factor of a data storage assembly.
 19. The apparatus of claim 10 wherein the first cover is characterized as an external cover, further comprising an internal cover enclosing the PCBA and contacting the heat conductor to conduct heat away from the heat conductor that is generated by the circuitry package.
 20. The apparatus of claim 19 further comprising the internal cover contacting the frame to conduct heat to the frame that is generated by the circuitry package.
 21. An apparatus comprising: a frame having a perimeter surface defining a passage; a printed circuit board assembly (PCBA) operably disposed within the passage, the PCBA including a printed circuit board and a circuitry package attached to one side of the printed circuit board, the circuitry package having a peripheral edge and a cap, the peripheral edge extending from a proximal end adjacent the printed circuit board to a distal end joined to the cap; a cover operably attached to the frame to enclose the PCBA; a thermal interface material (“TIM”) operably disposed between the cover and the PCBA, the TIM defining an opening that is sized to receivingly engage the circuitry package in a close mating engagement operably contacting the TIM simultaneously against the cap and the peripheral edge to conduct heat away from the circuitry package; and a heat conductor attached to the other side of the printed circuit board in an overlapping opposition to the circuitry package to conduct heat away from the printed circuit board that is generated by the circuitry package.
 22. A method comprising: obtaining a frame having a perimeter surface defining a passage; obtaining a printed circuit board assembly (PCBA) having a printed circuit board and a circuitry package attached to one side of the printed circuit board, the circuitry package having a peripheral edge and a cap, the peripheral edge extending from a proximal end adjacent the printed circuit board to a distal end joined to the cap; obtaining a thermal interface material (“TIM”) defining an opening that is sized to receivingly engage the circuitry package in a close mating engagement; positioning the TIM on the PCBA in the close mating engagement that contacts the TIM simultaneously against the cap and the peripheral edge; and attaching a cover to the frame to enclose the PCBA. 